Abstract

Introduction

To gain a better understanding of the clinical and economic outcomes associated with
methicillin-resistant Staphylococcus aureus (MRSA) infection in patients with early onset ventilator-associated pneumonia (VAP),
we retrospectively analyzed a multihospital US database to identify patients with
VAP over a 24 month period (2002–2003).

Method

Data recorded included physiologic, laboratory, culture, and other clinical variables
from 59 institutions. VAP was defined as new positive respiratory culture after at
least 24 hours of mechanical ventilation (MV) and the presence of primary or secondary
ICD-9-CM diagnosis codes of pneumonia. Outcomes measures included in-hospital morbidity
and mortality for the population overall and after onset of VAP (duration of MV, intensive
care unit [ICU] stay, in-hospital stay, and case mix and severity-adjusted operating
cost). The overall cost was calculated at the hospital level using the Center for
Medicare and Medicaid Services Cost/Charge Index for each calendar year.

Results

A total of 499 patients were identified as having VAP. S. aureus was the leading organism (31% of isolates). Patients with MRSA were significantly
older than patients with methicillin-sensitive Staphylococcus aureus (MSSA; median age 74 versus 67 years, P < 0.05) and more likely to be medical patients. Compared with MSSA patients, MRSA
patients on average consumed excess resources of 4.4 (95% confidence interval 0.6–8.2)
overall MV days, 3.8 (-0.5 to +8.0) days of inpatient length of stay (LOS), 5.3 (1.0–9.7)
ICU days, and US$7731 (-US$8393 to +US$23,856) total cost after controlling for case
mix and other factors. Furthermore, MRSA patients needed excess resources after the
onset of VAP (4.5 [95% confidence interval 1.0–8.1] MV days, 3.7 [-0.5 to +8.0] inpatient
days, and 4.4 [0.4–8.4] ICU days) after controlling for the same case mix and admission
severity covariates.

Conclusion

S. aureus remains a common cause of VAP. VAP due to MRSA was associated with increased overall
LOS, ICU LOS, and attributable ICU LOS compared with MSSA-related VAP. Although not
statistically significant because of small sample size and large variation, the attributable
excess costs of MRSA amounted to approximately US$8000 per case after controlling
for case mix and severity.